High prevalences of DAO enzyme deficiency based on alterations in the most common SNPs of the AOC1 gene have been reported in cohort studies of specific diseases, including a prevalence of 88 % in patients with at least moderate low urinary tract symptoms (LUTS) [18], 74.5 % in women with fibromyalgia [19], and 78.5 % in pediatric patients with attention deficit hyperactivity disorder (ADHD) [20]. This evidence concerns the gene AOC1 and attention deficit-hyperactivity disorder.